A flex cable is an impedance-controlled cable that is used to connect two components, such as printed circuit boards (PCBs), that are oriented in such a manner that directly connecting the components to each other is impractical. As the name implies, a flex cable is flexible and, thus, can be twisted and/or bent to accommodate interconnection of the components. Care must be taken, however, to ensure that such a flex cable is not bent beyond a minimum bend radius.
A typical flex cable is constructed of multiple layers of material, including a signal layer, a dielectric layer, and a power layer. The signal layer typically is formed of conductors, e.g., copper conductors, that are positioned in a generally planar arrangement, with each of the conductors being capable of carrying a separate signal. One or more dielectric layers surround the signal layer so that the conductors are spaced from the power layer, which functions as ground. Typically, the power layer is a thin plate of material, such as copper.
As the amount of material used in the signal and/or power layers of a flex cable increases, the resistance of the flex cable to bending and/or twisting also typically increases. This can be problematic, particularly when an increased amount of material is required to provide an appropriate number of conductors while attempting to provide enough flexibility for the intended application.